Conventionally, two different approaches have been used to attach a stock to the receiver of a shotgun. Each is associated with a type of action, which is the operating mechanism of the gun. The two types of actions are referred to as box lock and side lock.
The box lock action is a hammerless action commonly used in double barreled shotguns that dates back to 1875. The box lock action uses concealed, self-cocking hammers in a break-open action. A draw bolt opening within the stock receives the head of a draw bolt. The draw bolt is tightened to cause the stock to engage to the receiver and integrate the stock with the operative parts of the shotgun. An example of this approach, modified to reduce recoil, is found in U.S. Pat. No. 3,381,405 to Edwards. A sharp dividing line exists between the wooden stock and the metal, making this a typical consumer-level approach. Collectors of firearms do not like it because the appearance is bland.
The box lock action has two additional disadvantages: the hammer pin must be placed directly below the knee of the action, which is its weakest spot, and the action walls must be thinned out to receive locks. These are inserted from below into large slots in the action's body, which is then closed with a plate.
The side lock action is an expensive, high quality alternative to the box lock action. The moving parts of the action are located on side lock plates inletted in the stock. The side plates have holes that receive pins to mount the lock parts. The stock is deeply scalloped where it meets the action, with wood going over and under the side lock plates. The receiver has an upper and lower tang, which are portions of the receiver that extend rearwardly into the stock. Screws extend from the upper tang to the lower tang, compressing the stock between the tangs.
The side lock action is preferred by collectors because of its complexity and attractive appearance. However, the conventional side lock action also has drawbacks. The wooden stock can compress variably between the tangs, causing the flush fit between the tangs and the stock to be lost. The tang engagement screws also tend to back off over time, which causes the fit between the tangs and the stock to loosen. An imprecise fit between the stock and the tangs not only detracts from the shotgun's appearance, but may also compromise the stock's strength and the shotgun's accuracy.
It is therefore an object of this invention to provide to a side lock action firearm with an improved stock mounting system that enables the stock to fit flush with a side lock action without backing off or compressing irregularly.